Remember, 8 hp>4 def and 4 s.def on most pokemon. (not on pokemon who has wonderful hp but so-so or bad defences).

Also, on pokemon like dragonite, if you want to use special and physical attacks on him, try to give him a nature that boost the highest attack stat(atk in this case) and put EV's in the other (sp.atk).
This is because natures boosts by % and EV's by single points.